Method and apparatus for fabricating phosphor-coated LED dies

ABSTRACT

The present disclosure involves lighting apparatus. The lighting apparatus includes a light-emitting device. The light-emitting device includes a first doped semiconductor layer. A light-emitting layer is disposed over the first doped semiconductor layer. A second doped semiconductor layer is disposed over the light-emitting layer. The second doped semiconductor layer has a different type of conductivity than the first doped semiconductor layer. A photo-conversion layer is coated around the light-emitting device. A lens houses the light-emitting device and the photo-conversion layer within. The lens includes a first sub-layer and a second sub-layer. The first and second sub-layers have different characteristics.

PRIORITY DATA

The present application is a continuation-in-part (CIP) application ofU.S. patent application Ser. No. 13/788,536, filed on Mar. 7, 2013,entitled “Method and Apparatus for Packaging Phosphor-Coated LEDs” and acontinuation-in-part (CIP) application of U.S. application Ser. No.13/594,219, filed on Aug. 24, 2012, entitled “Method and Apparatus forFabricating Phosphor-Coated LED Dies”, the disclosures of each which arehereby incorporated by reference in their respective entireties.

TECHNICAL FIELD

The present disclosure relates generally to light-emitting devices, andmore particularly, to the fabrication of phosphor-coated light-emittingdiode (LED) dies.

BACKGROUND

LEDs are semiconductor photonic devices that emit light when a voltageis applied. LEDs have increasingly gained popularity due to favorablecharacteristics such as small device size, long lifetime, efficientenergy consumption, and good durability and reliability. In recentyears, LEDs have been deployed in various applications, includingindicators, light sensors, traffic lights, broadband data transmission,back light unit for LCD displays, and other suitable illuminationapparatuses. For example, LEDs are often used in illuminationapparatuses provided to replace conventional incandescent light bulbs,such as those used in a typical lamp.

To configure the color of the light output from an LED, aphotoconversion material such as phosphor may be utilized to change thelight output from one color to another. However, conventional methodsand techniques of applying photoconversion materials to LEDs suffer fromdrawbacks such as low throughput and high cost. In addition, someconventional LED packaging processes involve using a carrier substratefor support. As an LED dicing process is performed to singulate theLEDs, the carrier substrate is also sliced. This results in the waste ofthe carrier substrate, as the sliced carrier substrate may not be usedin fabrication again.

Therefore, although existing methods of applying photoconversionmaterials to LEDs have been generally adequate for their intendedpurposes, they have not been entirely satisfactory in every aspect. Acheaper and more efficient way of applying photoconversion materials toLEDs continues to be sought.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not necessarily drawn to scale oraccording to the exact geometries. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1-4 are diagrammatic fragmentary cross-sectional side views of aplurality of LEDs undergoing a packaging process according to someembodiments of the present disclosure.

FIGS. 5-8 are diagrammatic fragmentary cross-sectional side views of aplurality of LEDs undergoing a packaging process according to some otherembodiments of the present disclosure.

FIGS. 9-15 and 17-18 are diagrammatic fragmentary cross-sectional sideviews of a plurality of LEDs undergoing a packaging process according tovarious aspects of the present disclosure.

FIGS. 16A-16C are diagrammatic fragmentary cross-sectional side views ofdifferently-shaped side-lit batwing LED dies according to variousaspects of the present disclosure.

FIGS. 19A and 19B are a diagrammatic fragmentary top view and across-sectional view, respectively, of an embodiment of an LED lightingmodule according to various aspects of the present disclosure.

FIGS. 20-21 are diagrammatic fragmentary top views of variousembodiments of LED lighting modules according to various aspects of thepresent disclosure.

FIG. 22 is a diagrammatic fragmentary cross-sectional side view of anexample lighting apparatus according to various aspects of the presentdisclosure.

FIG. 23 is a diagrammatic fragmentary cross-sectional side view ofanother example lighting apparatus according to various aspects of thepresent disclosure.

FIG. 24 is a flowchart illustrating a method of packaging an LEDaccording to various aspects of the present disclosure.

FIG. 25 is a flowchart illustrating a method of packaging an LEDaccording to various aspects of the present disclosure.

FIGS. 26-33 and 35-36 are diagrammatic fragmentary cross-sectional sideviews of one or more LEDs undergoing a packaging process according tovarious embodiments of the present disclosure.

FIG. 34 is a diagrammatic perspective view of an LED die according tovarious embodiments of the present disclosure.

FIG. 37 is a flowchart illustrating a method of packaging an LEDaccording to various embodiments of the present disclosure.

FIG. 38 is a diagrammatic view of a lighting module that includes aplurality of phosphor-coated LED dies according to various embodimentsof the present disclosure.

DETAILED DESCRIPTION

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of variousembodiments. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed between the firstand second features, such that the first and second features may not bein direct contact. Moreover, the terms “top,” “bottom,” “under,” “over,”and the like are used for convenience and are not meant to limit thescope of embodiments to any particular orientation. Various features mayalso be arbitrarily drawn in different scales for the sake of simplicityand clarity. In addition, the present disclosure may repeat referencenumerals and/or letters in the various examples. This repetition is forthe purpose of simplicity and clarity and does not in itself necessarilydictate a relationship between the various embodiments and/orconfigurations discussed.

Semiconductor devices can be used to make photonic devices, such aslight-emitting diodes (LEDs). When turned on, LEDs may emit radiationsuch as different colors of light in a visible spectrum, as well asradiation with ultraviolet or infrared wavelengths. Compared totraditional light sources (e.g., incandescent light bulbs), lightinginstruments using LEDs as light sources offer advantages such as smallersize, lower energy consumption, longer lifetime, variety of availablecolors, and greater durability and reliability. These advantages, aswell as advancements in LED fabrication technologies that have made LEDscheaper and more robust, have added to the growing popularity ofLED-based lighting instruments in recent years.

As light sources, LED dies or emitters may not naturally emit the colorof light that is desirable for a lighting instrument. For example, manyLED emitters naturally emit blue light. However, it is desirable for anLED-based lighting instrument to produce a light that is closer to awhite light, so as to emulate the light output of traditional lamps.Therefore, photoconversion materials such as phosphor have been used toreconfigure the light output color from one to another. For example, ayellow phosphor material can change the blue light emitted by an LED dieto a color close to white.

However, traditional methods of applying photoconversion materials onLED dies have certain drawbacks. For example, these traditional methodsdo not offer the capability of applying the photoconversion material toLEDs on a die level or a chip level. As such, the traditional methods ofapplying photoconversion materials on LED dies may be expensive andinefficient. In addition, in certain LED packaging processes, thephosphor material may be coated on a plurality of LEDs disposed over acarrier substrate. As a dicing process is performed to separate the LEDsfrom adjacent LEDs (i.e., singulation), the carrier substrate underneathis also diced. The diced carrier substrate may not be reusable again.Thus, conventional LED packaging processes may lead to waste andinefficiencies in fabrication.

According to various aspects of the present disclosure, described belowis a method of applying a photoconversion material to LEDs on a dielevel or a chip level, which enhances throughput and reduces waste.Furthermore, a method of packaging phosphor-coated LEDs without wastingthe carrier substrate is also disclosed.

In more detail, FIGS. 1-8 are simplified diagrammatic cross-sectionalside views of a plurality of LEDs at various stages of packagingaccording to some embodiments of the present disclosure. Referring toFIG. 1, a submount 50 (also referred to as a substrate) is provided. Insome embodiments, the submount 50 may be a silicon submount. In otherembodiments, the submount 50 may be a ceramic submount or a printedcircuit board (PCB). The submount 50 provides mechanical strength andsupport for the subsequent packaging processes.

A plurality of conductive pads 60 is disposed on both sides of thesubmount 50. For example, the conductive pads 60A are disposed on afront side 70 of the submount 50, and the conductive pads 60B aredisposed on a back side 80 of the submount 50. The conductive pads60A-60B are thermally and electrically conductive. In some embodiments,the conductive pads 60A-60B include metal, for example copper, aluminum,or another suitable metal.

Each pair of the conductive pads 60A-60B is interconnected by arespective via 90 that extends through the substrate 50. The via 90contains a thermally and electrically conductive material as well, forexample a suitable metal material.

Referring now to FIG. 2, a solder paste 100 is applied on each of theconductive pads 60A from the front side 70. The solder paste 100 maycontain powdered metal solder in a viscous medium such as flux. Thesolder paste 100 is applied for bonding the conductive pads 60A to othercomponents, as discussed below.

A plurality of semiconductor photonic dies 110 are bonded to theconductive pads 60A through the solder paste 100. The semiconductorphotonic dies 110 function as light sources for a lighting instrument.The semiconductor photonic dies 110 are LED dies in the embodimentsdescribed below, and as such may be referred to as LED dies 110 in thefollowing paragraphs. As shown in FIG. 2, the LED dies 110 arephysically spaced apart from one another. In some embodiments, the LEDdies 110 are substantially evenly spaced apart from adjacent LED dies.

The LED dies 110 each include two differently doped semiconductorlayers. Alternatively stated, these oppositely doped semiconductorlayers have different types of conductivity. For example, one of thesesemiconductor layers contains a material doped with an n-type dopant,while the other one of the two semiconductor layers contains a materialdoped with a p-type dopant. In some embodiments, the oppositely dopedsemiconductor layers each contain a “III-V” family (or group) compound.In more detail, a III-V family compound contains an element from a “III”family of the periodic table, and another element from a “V” family ofthe periodic table. For example, the III family elements may includeBoron, Aluminum, Gallium, Indium, and Titanium, and the V familyelements may include Nitrogen, Phosphorous, Arsenic, Antimony, andBismuth. In certain embodiments, the oppositely doped semiconductorlayers include a p-doped gallium nitride (p-GaN) material and an n-dopedgallium nitride material (n-GaN), respectively. The p-type dopant mayinclude Magnesium (Mg), and the n-type dopant may include Carbon (C) orSilicon (Si).

The LED dies 110 also each include a light emitting layer such as amultiple-quantum well (MQW) layer that is disposed in between theoppositely doped layers. The MQW layer includes alternating (orperiodic) layers of active material, such as gallium nitride and indiumgallium nitride (InGaN). For example, the MQW layer may include a numberof gallium nitride layers and a number of indium gallium nitride layers,wherein the gallium nitride layers and the indium gallium nitride layersare formed in an alternating or periodic manner. In some embodiments,the MQW layer includes ten layers of gallium nitride and ten layers ofindium gallium nitride, where an indium gallium nitride layer is formedon a gallium nitride layer, and another gallium nitride layer is formedon the indium gallium nitride layer, and so on and so forth. The lightemission efficiency depends on the number of layers of alternatinglayers and thicknesses. In certain alternative embodiments, suitablelight-emitting layers other than an MQW layer may be used instead.

Each LED die may also include a pre-strained layer and anelectron-blocking layer. The pre-strained layer may be doped and mayserve to release strain and reduce a Quantum-Confined Stark Effect(QCSE)—describing the effect of an external electric field upon thelight absorption spectrum of a quantum well—in the MQW layer. Theelectron blocking layer may include a doped aluminum gallium nitride(AlGaN) material, wherein the dopant may include Magnesium. The electronblocking layer helps confine electron-hole carrier recombination towithin the MQW layer, which may improve the quantum efficiency of theMQW layer and reduce radiation in undesired bandwidths.

The doped layers and the MQW layer may all be formed by one or moreepitaxial growth processes known in the art. For example, these layersmay be formed by processes such as metal organic vapor phase epitaxy(MOVPE), molecular-beam epitaxy (MBE), metal organic chemical vapordeposition (MOCVD), hydride vapor phase epitaxy (HYPE), liquid phaseepitaxy (LPE), or other suitable processes. These processes may beperformed at suitable deposition processing chambers and at hightemperatures ranging from a few hundred degrees Celsius to over onethousand degrees Celsius.

After the completion of the epitaxial growth processes, an LED iscreated by the disposition of the MQW layer between the doped layers.When an electrical voltage (or electrical charge) is applied to thedoped layers of the LED 110, the MQW layer emits radiation such aslight. The color of the light emitted by the MQW layer corresponds tothe wavelength of the radiation. The radiation may be visible, such asblue light, or invisible, such as ultraviolet (UV) light. The wavelengthof the light (and hence the color of the light) may be tuned by varyingthe composition and structure of the materials that make up the MQWlayer. For example, the LED dies 110 herein may be blue LED emitters, inother words, they are configured to emit blue light.

As shown in FIG. 2, each LED die 110 also includes two conductiveterminals 120A and 120B, which may include metal pads. Each conductiveterminal 120A/120B is bonded to a respective one of the conductive pads60A (through the solder paste 100). Since the conductive pads 60A on thefront side 70 are electrically coupled to the conductive pads 60B on theback side 80, electrical connections to the LED dies 110 may beestablished through the conductive terminals 120A/120B from theconductive pads 60B. In the embodiments discussed herein, one of theconductive terminals 120A/120B is a p-terminal (i.e., electricallycoupled to the p-GaN layer of the LED die 110), and the other one of theconductive terminals 120A/120B is an n-terminal (i.e., electricallycoupled to the n-GaN layer of the LED die 110). Thus, an electricalvoltage can be applied across the terminals 120A and 120B (through theconductive pads 60B) to generate light a light output from the LED die110.

In certain embodiments, the LED dies 110 shown herein have alreadyundergone a binning process. In more detail, a plurality of LED dies hasbeen fabricated using standard LED fabrication processes. These LED diesmay have varying performance characteristics in different areas such aslight output intensity, color, current consumption, leakage, resistance,etc. A binning process involves dividing or assigning these LED diesinto different categories (or bins) according to each die's performancein these performance areas. For example, a bin 1 may include LED diesthat have a light output density that meets a predefined threshold, abin 10 may include LED dies that have serious performance failures andthus need to be discarded, so on and so forth. After the LED dies arebinned, a subset of the LED dies from one or more certain bins arechosen to be attached herein as the LED dies 110. The selected subset ofLED dies 110 may also be referred to as reconstructed LED dies.

Referring now to FIG. 3, a photoconversion material such as a phosphorfilm 150 is applied to the LED dies 110 collectively. In more detail,the phosphor film 150 is coated around the exposed surfaces of the LEDdies 110, as well as on the exposed surfaces of the conductive pads 60Aand the substrate 50. The phosphor film 150 may include eitherphosphorescent materials and/or fluorescent materials. The phosphor film150 is used to transform the color of the light emitted by an LED dies110. In some embodiments, the phosphor film 150 contains yellow phosphorparticles and can transform a blue light emitted by an LED die 110 intoa different wavelength light. By changing the material composition ofthe phosphor film 150, the desired light output color (e.g., a colorresembling white) may be achieved. The phosphor film 150 may be coatedon the surfaces of the LED dies 110 in a concentrated viscous fluidmedium (e.g., liquid glue). As the viscous liquid sets or cures, thephosphor material becomes a part of the LED package.

Wafer back side probing may also be performed at this stage. In otherwords, the LED dies 110 may be electrically accessed from the back side80 of the wafer through the conductive pads 60B. This back side probingprocess may be done to evaluate the light output performance from theLED dies 110, for example performance with respect to the colortemperature of the LED dies 110, etc. If the light output performance isunsatisfactory, the recipe for the phosphor material 150 may be modifiedto improve the light output performance.

Referring now to FIG. 4, a wafer dicing process is performed to the LEDdies 110 (and to the substrate 50 and the attached conductive pads 60).The wafer dicing process includes slicing portions of the phosphormaterial 150 between adjacent LED dies 110. The substrate 50 is alsosliced completely through from the front side 70 to the back side 80.Thus, as a result of the wafer dicing process, a plurality of LED chips160 is created by the sliced pieces of the LED dies 110 and the attachedportions of the substrate 50 and the conductive pads 60. Each LED chip160 may also be referred to as a single junction phosphor chip orpackage. The phosphor coating for these LED chips 160 is applied on adie level. In other words, the phosphor coating is collectively appliedto all the LED dies 110 before these LED dies are diced and undergoindividual package processing. As is shown in FIG. 4, the phosphormaterial is now conformally coated around each LED die 110. Theresulting LED chip 160 can achieve small dimensions too. In someembodiments, a footprint of the LED chip 160 ranges from about (1-2millimeters)×(1-2 millimeters).

FIGS. 5-8 are simplified diagrammatic cross-sectional side views of aplurality of LEDs at various stages of packaging according to somealternative embodiments of the present disclosure. For reasons ofclarity and consistency, similar components will be labeled the samethroughout the different embodiments illustrated in FIGS. 1-8. Referringto FIG. 5, a plurality of conductive pads 200 are provided without usinga substrate (such as the substrate 50 of FIG. 1). In some embodiments,the conductive pads 200 include lead frames, such as silver platting. Asolder paste 100 is applied on each conductive pad 200.

Referring now to FIG. 6, a plurality of LED dies 110 is bonded to theconductive pads 200 through the solder paste 100. As discussed above,these LED dies 110 may belong to a “binned” subset of a greater numberof LED dies. Each LED die 110 has two conductive terminals 120A and120B, one of which is the p-terminal, and the other one of which is then-terminal. Thus, electrical access to the LED die may be establishedthrough these terminals 120A/120B and the conductive pads 200electrically coupled to the terminals 120A/120B.

Referring now to FIG. 7, a photoconversion material 150 such as aphosphor film is coated around all the LED dies 110 collectively.Similar to the embodiments of FIGS. 1-4, the phosphor coating here isdone at a die level. Wafer probing may be performed at this stage inorder to tune the phosphor recipe.

Referring now to FIG. 8, a dicing process is performed to formindividual LED chips 160. As a part of the dicing process, the phosphormaterial 150 between adjacent LED dies 110 is sliced completely throughto separate the LED dies 110. In this manner, a plurality of singlejunction phosphor chips 160 is created. Each chip 160 includes an LEDdie 110 on which a phosphor film 150 is conformally coated. In someembodiments, a footprint of the chip 160 ranges from about (1-2millimeters)×(1-2 millimeters).

The embodiments of the present disclosure discussed above offeradvantages over existing methods. However, not all advantages arediscussed herein, other embodiments may offer different advantages, andthat no particular advantage is required for any embodiment.

One of the advantages of the embodiments of the present disclosure isthat the phosphor coating can be done at a die level. In other words,the phosphor coating can be applied to all the LEDs collectively. Aplurality of phosphor-coated LED dies is then formed by the subsequentdicing process. By doing so, the phosphor coating is fast and efficient,whereas conventional methods laborious processes that apply phosphor toeach LED die. Furthermore, since the embodiments of the presentdisclosure allow phosphor film to be conformally coated around each LEDdie, the photoconversion efficiency is improved, and very littlephosphor material is wasted. In comparison, some existing methods ofapplying phosphor to LED dies may result in a significant amount ofphosphor material being wasted. In addition, the embodiments of thepresent disclosure entail flexible processes that can be easilyintegrated into existing LED fabrication process flow.

FIGS. 9-15, 16A-16C, and 17-18 are simplified diagrammaticcross-sectional side views of a plurality of LEDs at various stages ofpackaging according to some embodiments of the present disclosure. Forreasons of consistency and clarity, similar components that appear inFIGS. 1-8 may be labeled the same in FIGS. 9-15, 16A-16C, and 17-18.Referring to FIG. 9, a substrate 300 is provided. The substrate 300 mayinclude a glass substrate, a silicon substrate, a ceramic substrate, agallium nitride substrate, or any other suitable substrate that canprovide mechanical strength and support. The substrate 300 may also bereferred to as a carrier substrate. A tape 305 is disposed on thesubstrate 300. In some embodiments, the tape 305 may contain an adhesivematerial. In yet other embodiments, a photoresist material may be usedin place of the tape 305. In further embodiments, an ultraviolet gel ora thermal curing gel may also be used in place of the tape 305.

A plurality of semiconductor photonic dies 110 are disposed on the tape305. The semiconductor photonic dies 110 function as light sources for alighting instrument. The semiconductor photonic dies 110 are LED dies inthe embodiments described below, and as such may be referred to as LEDdies 110 in the following paragraphs. As shown in FIG. 9, the LED dies110 are physically spaced apart from one another. In some embodiments,the LED dies 110 are substantially evenly spaced apart from adjacent LEDdies. The LED dies 110 are similar to the LED dies 110 discussed abovewith reference to FIGS. 2-8.

It is also understood that the spacing between adjacent LED dies 110 maybe tunable. In other words, depending on design requirements andmanufacturing concerns, the spacing between the adjacent LED dies 110may be increased or decreased prior to their disposition on the tape305. In certain embodiments, the spacing separating adjacent LED dies110 is in a range from about 0.5 mm to about 2 mm, for example about 1mm.

Referring now to FIG. 10, a photo-conversion material 350 such as aphosphor film is coated around all the LED dies 110 collectively. Inmore detail, the phosphor film 350 is coated around the exposed surfacesof the LED dies 110, as well as on the exposed surfaces of the tape 305and/or the substrate 300. The phosphor film 350 may include eitherphosphorescent materials and/or fluorescent materials. The phosphor film350 is used to transform the color of the light emitted by an LED dies110. In some embodiments, the phosphor film 350 contains yellow phosphorparticles and can transform a blue light emitted by an LED die 110 intoa different wavelength light. In other embodiments, a dual phosphor maybe used, which may contain yellow powder and red powder phosphor. Bychanging the material composition of the phosphor film 350, the desiredlight output color (e.g., a color resembling white) may be achieved. Insome embodiments, the phosphor film 350 includes at least two sub-layers(i.e., a composite layer structure). For example, one of thesesub-layers may contain a gel mixed with phosphor particles but notdiffuser particles, while the other one of these sub-layers may containa gel mixed with diffuser particles but not phosphor particles. Asanother example, one of these sub-layers may contain yellow phosphorparticles mixed with gel, while the other one of these sub-layers maycontain red phosphor particles mixed with gel.

The phosphor film 350 may be coated on the surfaces of the LED dies 110in a concentrated viscous fluid medium (e.g., liquid glue or gel). Incertain embodiments, the viscous fluid may include silicone epoxy andhave a refractive index in a range from about 1.4 to about 2. In someembodiments, diffuser particles may also be mixed in the viscous fluid.The diffuser particles may include, as examples, silica, PMMA, ZrO₂, orsilicon. In some other embodiments, one layer of the viscous fluid maybe mixed with the phosphor particles, while another layer of the viscousfluid may be mixed with the diffuser particles, and then one of the twolayers of the viscous fluid is applied over the other. Similarly, insome embodiments, one layer of the viscous fluid may be mixed withyellow phosphor, while the other layer of the viscous fluid may be mixedwith red phosphor. The phosphor film 350 is used herein to denote asingle layer of phosphor mixed with the gel, or multiple layers ofphosphor mixed with the gel. As the viscous liquid sets or cures, thephosphor material becomes a part of the LED package. In someembodiments, a curing temperature in a range between about 130 degreesCelsius to about 170 degrees Celsius is used.

Wafer probing may also be performed at this stage. In other words, theLED dies 110 may be electrically accessed through the conductiveterminals 120A and 120B. This wafer probing process may be done toevaluate the light output performance from the LED dies 110, for exampleperformance with respect to the color temperature of the LED dies 110,etc. If the light output performance is unsatisfactory, the recipe forthe phosphor material 350 may be modified to improve the light outputperformance.

Referring now to FIG. 11, the substrate 300 is removed. In someembodiments, the substrate 300 is removed through a laser lift-offprocess. In other embodiments, the substrate 300 may be removed using anetching process or another suitable process.

Thereafter, referring to FIG. 12, a dicing process 355 is performed tosingulate the LED dies 110. In some embodiments, the dicing process 355is performed using a die saw. In alternative embodiments, other suitablecutting/slicing means may be used. As a part of the dicing process 355,the phosphor material 350 between adjacent LED dies 110 is slicedcompletely through to separate the LED dies 110. In this manner, aplurality of single junction phosphor chips 160 (shown in FIG. 93) iscreated. Each chip 160 includes an LED die 110 surrounded by a phosphorfilm 350. In other words, the phosphor coating is collectively appliedto all the LED dies 110 before these LED dies are diced and undergoindividual package processing. The tape 305 is removed from each chip160. In some embodiments, a footprint of the chip 160 ranges from about(1-2 millimeters)×(1-2 millimeters).

In some scenarios, the tape 305 may become damaged while the substrate300 is removed (FIG. 11). In these cases, the damaged tape 305 may alsobe removed from the LED dies 110, and a new tape 365 may be used tore-tape the LED dies 110 before the dicing process 355 is performed, asshown in FIG. 14.

Regardless of whether the new tape 365 is used, it can be seen that thesubstrate 300 is removed before the dicing process 355 takes place. Bydoing so, several advantages are offered over existing methods, thoughit is understood that not all advantages are discussed herein, otherembodiments may offer different advantages, and that no particularadvantage is required for any embodiment. One advantage is that theremoval of the substrate 300 means that it is not cut or diced by thedicing process 355. Consequently, the substrate 300 is substantiallyunscathed and may be used again for future fabrication. For example, thesubstrate 300 may be used as a carrier substrate for a different batchof LED dies. The reusability of the substrate 300 reduces LEDfabrication costs. Another advantage is that, since the substrate 300need not be a part of the dicing process 355, the dicing process 355 canbe performed faster, which enhances the efficiency of the LED packaging.In addition, the embodiments of the present disclosure entail flexibleprocesses that can be easily integrated into existing LEDfabrication/packaging process flow.

FIGS. 15, 16A, 16B, 16C, and 17 are simplified diagrammaticcross-sectional side views of a plurality of LEDs at various stages ofpackaging according to some alternative embodiments of the presentdisclosure. For reasons of consistency and clarity, similar componentsappearing in FIGS. 9-17 will be labeled the same. Referring to FIG. 15,a plurality of LED dies 110 are disposed on the substrate 300. Aphosphor film 350 is also coated around the LED dies 110. Unlike theembodiment shown in FIGS. 9-14, however, the phosphor film 350 is shapedby a molding stencil 370. As a result of being shaped by the moldingstencil 370 and being cured, an upper surface 375A of the phosphor film350 exhibits a convex dome-like profile over each of the LED dies 110.In other words, for each LED die 110, there is a portion of the uppersurface 375 of the phosphor film 350 that is substantially rounded andcurved. This geometric configuration of the phosphor film 350 helpsfocus light emitted by the LED dies 110 underneath, thereby serving as alens for the LED dies 110.

It is understood that the dome-like profile for the phosphor film 350 ismerely an example. In other embodiments, different profiles may beachieved for the phosphor film 350 so that the phosphor film can furtherserve as a desired lens for the LED dies 110. For example, FIGS. 16A-Cillustrate different geometric profiles for the phosphor film 350. Forreasons of simplicity, each Figure only illustrate the geometric profilefor a single LED die 110, though it is understood that the same phosphorprofile is achieved for each of the plurality of LED dies 110. In FIG.16A, the phosphor film 350 is shaped (e.g., by a suitable moldingstencil) so that its upper surface 375B exhibits a concave V-shapeprofile. In FIG. 16B, the phosphor film 350 is shaped (e.g., by asuitable molding stencil) so that its upper surface 375C exhibits aconcave W-shape profile. In FIG. 16C, the phosphor film 350 is shaped(e.g., by a suitable molding stencil) so that its upper surface 375Dexhibits a concave U-shape profile.

As shown in FIGS. 16A-16C, a reflective layer 378 is formed over thesurfaces 375B/C/D of each of the phosphor films 150. The reflectivelayer 378 may contain a metal material such as silver or aluminum insome embodiments. The reflective layer 378 reflects radiation, forexample light emitted by the LED dies 110. Therefore, the light will notpropagate out upwards. Instead, the light will be propagated in asideways manner due to the presence of the reflective layer 378. Assuch, each of the phosphor profiles shown in FIGS. 16A-16C arecharacterized as side-lit batwing profiles. The LED dies 110 with thephosphor coatings (serving as lenses) shown in FIGS. 16A-16C are said tobe side-lit batwing emitters. In comparison, a lambertian emitter (e.g.,the LED die 110 with the dome-like phosphor shape shown in FIG. 15)emits light laterally as well as vertically (i.e., straight up).

One of the advantages of shaping the phosphor film 350 to have asuitable lambertian or side-lit batwing profile is that it iscost-effective to do so. Since the phosphor film 350 itself serves asthe lens, no additional secondary lenses are needed. In addition, theelimination of a potential secondary lens reduces a size of the LEDpackage, thereby making the overall package more compact. It isunderstood that additional phosphor profiles may be achieved, but theyare not specifically illustrated or discussed herein for reasons ofsimplicity. Further, for the sake of providing an illustration, theembodiment shown in FIGS. 16-17 and discussed below use a dome-likeprofile for the phosphor film 350, though it is understood that theother side-lit batwing profiles of FIGS. 16A-16C may be applicable aswell.

Referring now to FIG. 17, after the shaping and curing of the phosphorfilm 350, the substrate 300 is removed so as to preserve the substrate300 for future use. In some embodiments, the tape 305 need not beremoved. In other embodiments, the tape 305 is also removed, and a newtape 365 is then used to replace the removed tape 305. Thereafter, adicing process 355 is performed to singulate the LED dies 110. As aresult, individual LED chips 160 may be formed, as shown in FIG. 18.Once again, since the substrate 300 is removed before the dicingprocess, the substrate 300 may be reused for futurefabrication/packaging processes, thereby reducing packaging time andcost.

The singulated LED chips 160 shown in FIGS. 13 and 18 may be referred toas single junction LED chips. However, the concepts of the presentdisclosure may apply to multi-junction LED chips too. For example,referring now to FIG. 19A, a simplified diagrammatic top view of an LEDlighting module 380 is shown. The LED lighting module 380 includes aplurality of LED dies 110 arranged in a row. The LED dies 110 haveundergone a packaging process similar to those discussed above withreference to FIGS. 9-18. However, unlike the embodiments associated withFIGS. 9-18, the LED dies 110 are not singulated into individual LEDchips. Instead, the dicing process is performed so that a plurality ofthem (i.e., the row of LEDs) are kept together and not diced. Toaccomplish this, the dicing process may be performed in only onedirection (e.g., dicing only horizontally or only vertically) so that amatrix of LED dies are diced into a plurality of rows (or a plurality ofcolumns) of LED dies. Alternatively, two dimensional dicing may still beemployed, but a predetermined number of LED dies in a row (or column)will not undergo dicing for the LED dies in the row (or column), thoughthese LED dies are still separated from adjacent rows (or columns) ofLED dies by dicing. Once again, the substrate 300 is removed before thedicing process is performed, thereby allowing the substrate 300 to bereused. A phosphor film 350 may be coated over the row of LED dies 110.In any case, the row of LED dies 110 in the LED lighting module 380 maybe disposed on a board 385, such as a printed circuit board (PCB).

It is understood that, with transmitting or diffusive housing, aluminaire of a T5 or T8 type light tube incorporating light module 380can easily be formed. For example, referring to FIG. 19B, a simplifiedcross-sectional side view of a T5 or T8 type of light tube 386 isillustrated. The light tube 386 has a housing 387, which may beapproximately circular or round. The housing 387 provides a cover andprotection for the light-emitting elements housed therein, for examplethe phosphor-coated LED dies 110 discussed above (only one of which isshown in the cross-sectional view herein). For example, the LED dies 110are implemented as the lighting module 380 shown in FIG. 19A, which isdisposed on a PCB board 385. The PCB board 385 may be thermalconductively coupled to a heat sink 388. Once again, the phosphor coatedLED dies 110 do not need a secondary lens, since the phosphor may bemolded into a suitable shape to function as a suitable lens. Therefore,the light tube 386 may be flexibly configured to have a desired type oflight output.

FIG. 20 illustrates a simplified diagrammatic top view of another LEDlighting module 390 having a plurality of LED dies 110 arranged in amatrix (i.e., rows and columns). These LED dies 110 have been singulatedwithout dicing the carrier substrate. A phosphor film 350 may be appliedto the LED dies 110 before the dicing process. After the dicing process,each LED die 110 is coated around with phosphor film 350. The LED dies110 may then be placed on the board 385, such as a PCB.

FIG. 21 illustrates a simplified diagrammatic top view of yet anotherLED lighting module 400 having a plurality of LED dies 110 arranged in amatrix (i.e., rows and columns). These LED dies 110 have been singulatedwithout dicing the carrier substrate. Furthermore, these LED dies 110may be formed as an array of LEDs. In other words, in the dicingprocess, these LED dies 110 are kept together (no dicing to separatethem from one another), while they are collectively separated from otherLED arrays. A phosphor film 350 may be collectively applied to all ofthe LED dies 110 before the dicing process. After the dicing process,the array of LED dies collectively is coated around with the phosphorfilm 350. The LED dies 110 may then be placed on the board 385, such asa PCB.

Similarly, if LED dies 110 disposed on a board 385 are in the shape of amatrix, with the transmitting or diffusing housing (for example ahousing similar to the housing 387 of FIG. 19B) a luminaire of lightbulbs (including MR series bulbs), par light, or down lightincorporating light module 390 or 200 can easily be formed, too. Forreasons of simplicity, the specific types of luminaires are notspecifically illustrated herein.

Referring now to FIG. 22, discussed below is an example multi-chiplighting unit 440A using the LED chips 160 according to variousembodiments of the present disclosure. The lighting unit 440A includes asupport member 450. In some embodiments, the support member 450 includesa Metal Core Printed Circuit Board (MCPCB). The MCPCB includes a metalbase that may be made of Aluminum (or an alloy thereof). The MCPCB alsoincludes a thermally conductive but electrically insulating dielectriclayer disposed on the metal base. The MCPCB may also include a thinmetal layer made of copper that is disposed on the dielectric layer. Inother embodiments, the support member 450 may include other suitablematerials, for example ceramic, copper, or silicon. The support member450 may contain active circuitry and may also be used to establishinterconnections.

As the name implies, the multi-chip lighting unit 440A includes aplurality of LED dies 110. The LED dies 110 are parts of the singlejunction phosphor-coated LED chips 160 discussed above. For reasons ofsimplicity, the conductive terminals of the LED chips 160 are not shownherein. In the embodiments discussed herein, the LED dies 110 arephysically spaced apart from one another.

The lighting unit 440A also includes a diffuser cap 460. The diffusercap 460 provides a cover for the LED dies 110 located on the supportmember 450. Stated differently, the LED dies 110 may be encapsulated bythe diffuser cap 460 and the support member 450 collectively. Thesupport member 450 may or may not be completely covered by the diffusercap 460. In some embodiments, the diffuser cap 460 has a curved surfaceor profile. In some embodiments, the curved surface may substantiallyfollow the contours of a semicircle, so that each beam of light emittedby the LED dies 110 may reach the surface of the diffuser cap 460 at asubstantially right incident angle, for example, within a few degrees of90 degrees. The curved shape of the diffuser cap 460 helps reduce TotalInternal Reflection (TIR) of the light emitted by the LED dies 110. Insome embodiments, the diffuser cap 460 has a textured surface forfurther scattering of the incident light.

In some embodiments, the space between the LED dies 110 and the diffusercap 460 may be filled by an optical-grade silicone-based adhesivematerial 470, also referred to as an optical gel 470. Diffuser particlesmay be mixed within the optical gel 470 in these embodiments so as tofurther diffuse light emitted by the LED dies 110. In other embodiments,the space between the LED dies 110 and the diffuser cap 460 may befilled by air.

The support member 450 is located on a thermal dissipation structure500, also referred to as a heat sink 500. The heat sink 500 is thermallycoupled to the LED dies 110 through the support member 450. The heatsink 500 is configured to facilitate heat dissipation to the ambientatmosphere. The heat sink 500 contains a thermally conductive material,such as a metal material. The shape and geometries of the heat sink 500may be designed to provide a framework for a familiar light bulb whileat the same time spreading or directing heat away from the LED dies 110.To enhance heat transfer, the heat sink 500 may have a plurality of fins510 that protrude outwardly from a body of the heat sink 500. The fins510 may have substantial surface area exposed to ambient atmosphere tofacilitate heat transfer. In some embodiments, a thermally conductivematerial may be disposed between the substrate and the heat sink 500.For example, the thermally conductive material may include thermalgrease, metal pads, solder, etc. The thermally conductive materialfurther enhances heat transfer from the LED dies 110 to the heat sink500.

In addition to a multi-chip lighting instrument, the concepts of thepresent disclosure may also apply to a single-chip lighting unit, forexample a single-chip lighting unit 440B shown in FIG. 23. Instead ofusing a plurality of LED chips 160 as light sources (such as themulti-chip lighting instrument 240A of FIG. 22), the single-chiplighting unit 440B includes a single LED chip 160 to generate light.Similar to the multi-chip lighting unit 440A, the single-chip lightingunit 240B includes a support member 450 for housing additionalelectronic circuitry and providing interconnections, a diffuser cap 460for optical considerations, an optical gel 470 disposed between thediffuser cap 460 and the support member 450, and a heat sink 500 forthermal dissipation. The single-chip lighting unit 440B may includeadditional components for facilitating light output, but theseadditional components are not discussed in detail herein for reasons ofsimplicity.

FIG. 24 is a flowchart of a method 600 for packaging an LED according tovarious aspects of the present disclosure. The method 600 includes astep 610, in which a plurality of LEDs is provided. The LEDs aredisposed over an adhesive tape. The tape is disposed on a substrate. Insome embodiments, the substrate includes one of: a glass substrate, asilicon substrate, a ceramic substrate, and a gallium nitride substrate.In some embodiments, the LEDs are selected from a group of LEDs that areassociated with a plurality of bins. The plurality of LEDs that areselected all belong to a subset of the plurality of bins.

The method 600 includes a step 620, a phosphor layer is coated over theplurality of LEDs. The phosphor layer may include a yellow phosphor or acombination of yellow and red phosphor particles. The phosphor particlesmay be mixed in a viscous fluid. In some embodiments, the viscous fluidmay also contain diffuser particles.

The method 600 includes a step 630, in which the phosphor layer iscured. The curing of the phosphor layer helps it maintain a desiredshape. In some embodiments, the curing is performed at a hightemperature, for example a temperature in a range from about 130 degreesCelsius to about 170 degrees Celsius.

The method 600 includes a step 640, in which the tape and the substrateare removed.

The method 600 includes a step 650, in which a replacement tape isattached to the plurality of LEDs.

The method 600 includes a step 660, in which a dicing process isperformed to the plurality of LEDs after the substrate has been removed.Therefore, the dicing process does not involve dicing the substrate.

The method 600 includes a step 670, in which the removed substrate isrecycled or reused for a future LED packaging process. In other words,the removed substrate can be used as a carrier substrate for a differentplurality of LEDs that need to be packaged.

Additional processes may be performed before, during, or after theblocks 610-670 discussed herein to complete the fabrication of thelighting apparatus. For example, in some embodiments, the method 600 mayinclude a step of molding the phosphor layer such that the phosphorlayer has a plurality of segments that each have a dome-like profile ora concave V-shape, U-shape, or W-shape profile. Each of these segmentsis disposed over a respective one of the LEDs. These segments serve aslenses for the LEDs underneath. For reasons of simplicity, otheradditional processes are not discussed herein.

FIG. 25 is a flowchart of a method 700 for packaging an LED according tovarious aspects of the present disclosure. The method 700 includes astep 710, in which a group of metal pads and a group of LEDs areprovided. In some embodiments, the group of LED is provided by:obtaining a plurality of LEDs, followed by assigning the plurality ofLEDs into different bins according to their performance characteristics,and then choosing one or more bins of LEDs as the group of LEDs. In someembodiments, the metal pads are lead frames.

The method 700 includes a step 720, in which the group of LEDs isattached to the group of metal pads. Each LED is spaced apart fromadjacent LEDs. In some embodiments, the step 720 is performed so thateach LED is attached to two of the respective metal pads that arephysically separated from each other. For each LED, one of the two metalpads is attached to a p-terminal of the LED, and the other one of thetwo metal pads is attached to an n-terminal of the LED.

The method 700 includes a step 730, in which a phosphor film is coatedaround the group of LEDs collectively. The phosphor film is coated ontop and side surfaces of each LED and between adjacent LEDs. The method700 includes a step 740, in which a dicing process is performed to dicethrough portions of the phosphor film located between adjacent LEDs, soas to divide the group of LEDs into a plurality of individualphosphor-coated LEDs.

Additional processes may be performed before, during, or after theblocks 710-740 discussed herein to complete the fabrication of thelighting apparatus. For the sake of simplicity, these additionalprocesses are not discussed herein.

FIGS. 26-36 are simplified diagrammatic cross-sectional side views andperspective views of one or more LEDs at various stages of asubstrate-less packaging process according to some embodiments of thepresent disclosure. For reasons of consistency and clarity, similarcomponents appearing in FIGS. 1-36 will be labeled the same.

Referring to FIG. 26, the plurality of LED chips 160 is provided. TheLED chips 160 have already undergone the phosphor-coating and dicingprocesses discussed above with reference to FIGS. 9-13. A carriersubstrate 300 is also provided. As discussed above, the carriersubstrate 300 may include a glass substrate, a silicon substrate, aceramic substrate, a gallium nitride substrate, or any other suitablesubstrate that can provide mechanical strength and support. In someembodiments, the carrier substrate 300 is the same substrate 300 thatwas used in the phosphor coating of the LED chips 160 and that wasremoved in FIG. 11. In other embodiments, the carrier substrate 300 is asubstrate similar to the carrier substrate 300 that was removed in FIG.11, but not the same.

The LED chips 160 are attached to the substrate 300 through a tape 305.In some embodiments, the tape 305 may be a double-sided tape. In otherembodiments, instead of using the tape 305, an adhesive material or aphotoresist material may be used to help attach the LED chips 160 to thesubstrate 300.

Referring now to FIG. 27, a plurality of lenses 800 are formed. In someembodiments, the lenses 800 are formed by a molding process. Forexample, a gel may be applied over the substrate 300 and then molded bya molding apparatus similar to the molding stencil 370 shown in FIG. 15.In some embodiments, the gel can be a high transmittance material, forexample a material having a transmittance that is greater than about90%. The gel material may also have a suitable refractive index, forexample a refractive index in a range from about 1.4 to about 2.Diffuser particles may also be added to, or mixed within, the gel. Insome embodiments, the diffuser particles have a refractive index in arange from about 1.4 to about 2. The diffuser particles may include, asnon-limiting examples, silica, pmma, ZrO₂, or silicon. After beingmolded, the gel material may also be cured.

As a result of being shaped by the molding apparatus and being cured, anupper surface of each of the lenses 800 may achieve any desired profile.In the embodiment shown in FIG. 27, the lenses 800 may each have aconvex dome-like profile. In other words, for each lens 800, there is aportion of the upper surface that is substantially rounded and curved.In some embodiments, the lenses 800 are shaped as a hemisphere or asemi-ellipsoid. Such geometric configurations of the lenses help focuslight emitted by the LED dies 110 underneath.

It is understood that the dome-like profile for the lenses 800 is merelyan example. In other embodiments, different profiles may be formed forthe lenses 800 to achieve different optical purposes. For example, FIG.28 illustrates a different geometric profile for the lenses 800. In theembodiment shown in FIG. 28, the lenses 800 each include a recess 810located over the LED die 110, so that the lenses 800 may achieve a“batwing-like” design. In the embodiment shown in FIG. 28, the recess810 may resemble an inverted cone, which correspondingly has across-sectional profile that resembles an inverted triangle. Thespecific geometries and dimensions of the cone (or triangle in thecross-sectional view) may be tuned by configuring the molding apparatusappropriately. In yet other embodiments, the lenses 800 may be shapeddifferently to achieve other geometric profiles. For example, the lenses800 may be shaped to have a concave W-shaped profile or a concaveU-shaped profile in other alternative embodiments.

The lenses 800 may also be formed to have specific dimensions. This maybe achieved by configuring the dimensions of the molding apparatus, forexample. In some embodiments, the lenses 800 are taller (i.e.,vertically) than their respective LED dies by greater than about 100microns. In some embodiments, the lenses 800 are wider (i.e., laterallyor horizontally) than their respective LED dies by greater than about 15microns.

It is also understood that the lenses 800 may also be formed to havemultiple layers. For example, referring now to FIG. 29, the lenses 800may each include a sub-layer 800A and a sub-layer 800B disposed over thesub-layer 800A. In some embodiments, the sub-layer 800A is mixed withphosphor particles but not diffuser particles, and the sub-layer 800B ismixed with diffuser particles but not phosphor particles. In otherembodiments, the sub-layer 800B is mixed with phosphor particles but notdiffuser particles, and the sub-layer 800A is mixed with diffuserparticles but not phosphor articles. The sub-layers 800A and 800B mayalso each be mixed with different color phosphor particles. For example,the sub-layer 800A may be mixed with yellow phosphor particles, and thesub-layer 800B may be mixed with red phosphor particles, or vice versa.In further alternative embodiments, the lenses 800 may include more thantwo sub-layers that may each have its own characteristics or materialcompositions, although these embodiments are not specificallyillustrated herein for reasons of simplicity.

Regardless of how the lenses 800 are molded, a dicing process isperformed to separate adjacent LED dies 110 (with their respectivelenses 800 formed thereon) from other adjacent LED dies. An embodimentof the dicing process is illustrated in FIG. 30 as dicing or singulationprocess 820. In some embodiments, the dicing process 820 may involve theuse of a mechanical sawing blade. In other embodiments, the dicingprocess 820 may involve the use of a laser.

Referring now to FIG. 31, the tape 305 and the substrate 300 areremoved. This may be referred to as a de-taping process. In someembodiments, the de-taping process may also involve replacing theremoved tape 305 with a new tape. In other embodiments, the tape 305need not be removed. As a result of the singulation and de-tapingprocesses, individual LED chips 160 are formed. It is understood thatthe singulation process 820 need not be performed before the de-tapingprocess. In some embodiments, the de-taping process may be performedfirst to remove the substrate 300 and/or the tape 305, and thereafterthe singulation process 820 may be performed to separate adjacent LEDdies 110 from one another. By doing so, the removed substrate 300 may bereused for future fabrication/packaging processes, thereby reducingpackaging time and cost.

The singulated LED chips 160 (with the lenses 800 formed thereon) shownin FIG. 31 may be referred to as single junction LED chips. However, theconcepts of the present disclosure may also apply to multi-junction LEDchips discussed above and shown in FIGS. 19A/B and 20-22. In thismanner, a matrix of LED dies (containing one or more rows and one ormore columns of LED dies) may be formed as part of a lighting module,for example a lighting module 830 shown in FIG. 32. The lighting module830 includes a row of LED chips 160 that are bonded to a substrate 450(i.e., the support member 450 discussed above with reference to FIGS.22-23), which may include a MCPCB in some embodiments. In otherembodiments, the substrate 450 may include a copper substrate or aceramic substrate. The lighting module 830 may also include a heat sink(not shown herein), such as the heat sink 500 in FIGS. 22-23. Thelighting module 830 may be implemented in a suitable lighting product,such as an indoor A lamp, a T-5 tube, a T-8 tube, etc. The lightingproduct may be configured to have a single color temperature (CCT) or acombination of color temperatures, for example by tuning the wavelengthof the light emitted by one or more of the LED dies 110 and/or tuningthe material compositions of the phosphor particles in the film 350and/or the lenses 800.

Due to the unique fabrication process flow of the present disclosurediscussed above, the LED chips 160 formed herein have various structuraldifferences compared to conventional LED chips. For example, referringto FIG. 33, a more detailed cross-sectional view of an LED chip 160 isillustrated according to some embodiments of the present disclosure. TheLED chip 160 includes an LED die 110 and a phosphor film 350 coated onthe top surface and side surfaces of the LED die 110. As discussedabove, the phosphor film 350 is formed by applying a phosphor-containingmaterial (e.g., a gel) on a plurality of LED dies 110 and thereaftersingulating the LED dies by a dicing process. The phosphor film 350coated around each LED die 110 has side surfaces 850 and a top surface851. Due to the dicing process, the side surfaces 850 of the phosphorfilm 350 are substantially planar or flat. For example, the planar orflat side surfaces 850 of the phosphor film 350 may be defined by amechanical sawing blade or a concentrated laser beam used to carry outthe dicing process. In comparison, the phosphor film coated aroundconventional LED dies may not have flat side surfaces, since thephosphor material is typically coated on each LED die individually anddoes not undergo the dicing process discussed above. As a result,conventional LED dies may have more rounded or curved side surfaces.

Compared to the side surfaces 850, the top surface 851 of the LED chip160 is not as flat or planar, since the top surface 851 is not definedby a dicing process. For example, in some embodiments, the top surface851 has a surface topography variation of about +/−50 microns, whereasthe side surfaces 850 has a surface topography variation of about +/−5microns. To the human eye, the top surface 851 may appear as asubstantially flat surface. But when examined closely by a machine(e.g., under a microscope, etc.), the different surface roughnesscharacteristics between the top surface 851 and the side surfaces 850 ofthe phosphor film 350 will become apparent. Again, these differentroughness characteristics are a consequence of the unique fabricationprocess flow discussed herein. The side surfaces 850 are formed bydicing of cutting, and thus the side surface roughness is defined atleast in part by the planarity of the blade (or laser) used to performthe cutting. On the other hand, the top surface 851 is not formed by acutting or dicing process but by deposition, and thus the top surfaceroughness is defined by the phosphor deposition processes. Thus, inaddition to the differences in topography variations discussed abovebetween the top and side surfaces 851 and 850, there may be otherdistinguishable differences that are not necessarily visible to a humaneye but are clearly identifiable when examined closely using a machine.

In addition to the planar of flat side surfaces 850, the phosphor film350 of the embodiment of the LED chip 160 shown in FIG. 33 has one ormore sharp or angular corners 860 that are located above the LED die110. These angular corners 860 are defined by the side surfaces 850 andthe top surface 851. A simplified three-dimensional (3D) perspectiveview of the angles 860 is illustrated in FIG. 34 to facilitate a betterunderstanding of the present disclosure. In more detail, FIG. 34 is asimplified 3-D perspective view of a phosphor-coated LED die. Thus, thesurfaces shown in FIG. 34 are surfaces of the phosphor film 350. As canbe seen, each angular corner 860 is defined by the substantiallystraight edges of the side surfaces 850 and the edges of the top surface851 of the phosphor film. In some embodiments, the corner 860 mayinclude a pointy vertex, or an apex, which is an intersection of theedges of the top and side surfaces 851/850. Again, such sharp or angularcorners 860 of the present disclosure is a result of the uniquefabrication process flow discussed above, for example a result of thedicing process used to singulate the phosphor-coated LED dies.Conventional LED dies may have a phosphor film coated thereon, but dueto their fabrication process flows, the phosphor film coated onconventional LED dies are devoid of such angular corners or apexes.

As shown in FIGS. 33-34, the angular corner 860 may have an angle 870.In the embodiment shown in FIGS. 33-34, the angle 870 is about 90degrees. This corresponds to the dicing process being performedsubstantially perpendicularly with respect to the top surface 851 of thephosphor film 350. In other words, the dicing process is performed“straight down” without a tilt angle. However, the dicing process may beperformed with a tilt angle in some embodiments, which would result inthe angle 870 of the corner 860 being greater than about 90 degrees, asis shown in FIG. 35. The angle 870 may range from about 90 degrees toabout 135 degrees. It is understood that the specific shape and geometryof the mechanical sawing blade may also contribute to the angle 870being greater than about 90 degrees.

FIG. 36 illustrates another structural difference between the LED chips160 of the embodiments of the present disclosure and conventional LEDchips. Due to the unique fabrication process flow discussed above, a gap900 will exist between the upper surface of the substrate 450 (forexample a MCPCB) and the phosphor film 350. In more detail, the LEDchips 160 are bonded to the substrate 450 (e.g., a MCPCB) after thephosphor film 350 has been coated thereon. To facilitate the bonding ofthe LED chips to the substrate 450, solder is applied on the uppersurface of the substrate 450 and undergoes a solder reflow process. Inother words, solder serves as a physical and electrical interfacebetween each LED chip 160 and the substrate 450. This solder materialhas a certain height, however, and it is the height of the soldermaterial that contributes to the gap 900. For reasons of simplicity, thesolder is not specifically illustrated herein, but it is understood thatportions of the conductive terminals 120A/120B include the solder. Incomparison, according to conventional methods, a phosphor film istypically coated to LEDs after the LEDs have been attached to asubstrate. As such, the phosphor film is applied in a manner such thatit comes into contact with the upper surface of the substrate. Hence,there is no gap similar to the gap 900 herein in LEDs fabricated byconventional phosphor coating methods.

As shown in FIG. 36, the gap 900 has a vertical dimension (i.e., height)910. In some embodiments, the vertical dimension 910 is in a range fromabout 0.1 micron to about 50 microns, for example in a range from about40 microns to about 50 microns. Again, since the gap 900 is caused bythe height of the solder material that is used to bond the LED chip 160to the substrate 450, it may be said that the vertical dimension 910 isroughly equal to the height of the solder material. Meanwhile, thephosphor film 350 has a lateral dimension 911 that is in a range fromabout 60 microns to about 200 microns, for example about from 100microns to about 150 microns, and the phosphor film 350 also has avertical dimension 912 that is in a range from about 300 microns toabout 1000 microns, for example about from 400 microns to about 600microns.

In more detail, the LED die includes doped semiconductor layers 920 and930, and a light-emitting layer 940 disposed between the dopedsemiconductor layers 920 and 930. In some embodiments, the dopedsemiconductor layers 920 and 930 contain III-V group compounds, such asGaN. The layers 920 and 930 have different types of conductivity (i.e.,one of them is n-doped, and the other is p-doped). The light-emittinglayer 940 may include a multiple quantum well (MQW). The conductiveterminal 120A is electrically coupled to the doped semiconductor layer930, while the conductive terminal 120B is electrically coupled to thedoped semiconductor layer 920. In various embodiments, the conductiveterminals 120A and 120B may each include one or more metal pads, solder,or other types of electrical interconnections. It is understood that theLED die illustrated in FIG. 36 is simplified for reasons of simplicity.For example, the LED die may include additional unillustrated un-dopedlayers, buffer layers, barrier layers, passivation layers, etc. Inaddition, the embodiment of the LED die illustrated in FIG. 36 is ahorizontal LED die, though some of the concepts of the presentdisclosure may apply to a vertical LED die as well.

In any case, it can be seen that the gap 900 is defined at least in partby a bottommost surface 950 (from the portion of the phosphor film 350disposed on side surfaces or sidewalls of the LED die) of the phosphorfilm 350 and an upper surface 960 of the substrate 450. Stateddifferently, the bottommost surface 950 of the phosphor film 350 isseparated from the substrate 450, and the phosphor film 350 does notcompletely cover up the side surfaces or sidewalls of the LED die. Itmay also be said that the bottommost surface 950 is located above thebottom surfaces of the conductive terminals 120A/120B, or the bottommostsurface 950 of the phosphor film 350 is located closer (i.e., higher upto the doped semiconductor layer 920 than the bottom surfaces of theconductive terminals 120A/120B). It is understood that although theembodiment shown in FIG. 36 illustrates the sidewalls of the conductiveterminals 120A/120B as being substantially co-planar with the sidewallsof the rest of the LED chip 160, it is not necessarily true in otherembodiments. For example, in some embodiments, a gap of between about0.1 microns to about 5 microns may exist between the sidewall of the LEDchip 160 and the sidewall of the conductive terminals 120A/120B.

FIG. 37 is a simplified flowchart illustrating a method 1000 ofpackaging light-emitting devices. The method 1000 includes a step 1010of providing a substrate having a layer disposed thereon. In someembodiments, the providing of the layer comprises placing a tape on thesubstrate. In some embodiments, the providing of the layer includesforming a photoresist material on the substrate. In some embodiments,the providing of the layer comprises forming an adhesive layer on thesubstrate.

The method 1000 includes a step 1020 of attaching a plurality oflight-emitting devices to the layer.

The method 1000 includes a step 1030 of applying a gel over thesubstrate, the gel covering the plurality of light-emitting devices.

The method 1000 includes a step 1040 of shaping the gel into a pluralityof lenses, wherein the lenses each cover a respective one of thelight-emitting devices.

In some embodiments, the applying of the gel in step 1030 and theshaping of the gel in step 1040 are performed such that: the lenses eachinclude a first sub-layer and a second sub-layer, and the first andsecond sub-layers have different characteristics. In some embodiments,the first sub-layer contains phosphor particles, and the secondsub-layer contains diffuser particles. In some embodiments, the firstsub-layer contains first phosphor particles, and the second sub-layercontains second phosphor particles, and the first and second phosphorparticles are different color phosphor particles.

The method 1000 includes a step 1050 of separating the light-emittingdevices from one another. In some embodiments, the step 1050 includes adicing process.

The method 1000 includes a step 1060 of removing the substrate and thelayer. In some embodiments, the step 1060 includes a de-taping process.

The method 1000 includes a step 1070 of bonding the separatedlight-emitting devices to a printed circuit board.

It is understood that the steps 1010-1070 are not necessarily performedsequentially unless otherwise specified. For example, the separating ofthe light-emitting devices may be performed before the removing of thesubstrate in some embodiments, and the separating of the light-emittingdevices is performed after the removing of the substrate in otherembodiments. It is also understood that additional steps may beperformed before, during, or after the steps 1010-1070 discussed above.For example, before the step 1020 of attaching of the plurality oflight-emitting devices, the method 1000 may include a step of coating aphosphor layer on the light-emitting devices. For reasons of simplicity,other steps are not discussed in detail herein.

FIG. 38 illustrates a simplified diagrammatic view of a lighting systemor lighting apparatus 1500 that includes some embodiments of the LEDdies 110 or LED chips 160 discussed above. For example, the LED dies 110or LED chips 160 may be implemented as a part of the lighting unit 440Adiscussed above, which can then be implemented in the lighting apparatus1500. The lighting apparatus 1500 has a base 1510, a body 1520 attachedto the base 1510, and a lighting assembly 1530 attached to the body1520. In some embodiments, the lighting assembly 1530 is a down lamp (ora down light lighting module). In other embodiments, the lightingassembly 1530 may be another type of light, such as a par light or alight tube. The lighting assembly 1530 may be used for in-door lightingor out-door lighting, such as a street lamp or road lamp.

The lighting assembly 1530 can include the lighting unit (e.g., 240A or240B) or light module (e.g., 380, 390, or 400) discussed above withreference to FIGS. 1-37. In other words, the lighting assembly 1530 ofthe lighting apparatus 1500 includes an LED-based light source, whereinthe LED dies are phosphor coated in a localized manner. The LEDpackaging for the lighting assembly 1530 is configured to produce alight output 1540. It is also understood that in certain embodiments,light modules not using an optical gel or a diffuser cap may also serveas a light source (e.g., the lighting assembly 1530) for the lightingapparatus 1500.

One of the broader forms of the present disclosure involves a method.The method involves: bonding a plurality of light-emitting dies to aplurality of conductive pads; applying a phosphor material on theplurality of light-emitting dies in a manner such that spaces betweenadjacent light-emitting dies are filled with the phosphor material; andseparating the plurality of light-emitting dies from one another,thereby forming a plurality of phosphor-coated light-emitting dies,wherein each light-emitting die has the phosphor material coated on atop surface and side surfaces of the light-emitting die.

In some embodiments, the bonding is performed so that the plurality oflight-emitting dies are physically spaced apart from one another; andthe separating includes dicing the phosphor materials that fill thespaces between the adjacent light-emitting dies.

In some embodiments, the bonding is performed so that eachlight-emitting die is bonded to two of the respective conductive padsthat are spaced apart from one another. In some embodiments, eachlight-emitting die includes a p-terminal and an n-terminal; thep-terminal is bonded to one of the conductive pads; and the n-terminalis bonded to the other one of the conductive pads.

In some embodiments, the method further includes: before the bonding,performing a binning process to a further plurality of light-emittingdies; and selecting, in response to results of the binding process, asubset of the further plurality of the light-emitting dies as theplurality of the light-emitting dies for bonding.

In some embodiments, the method further includes: fabricating a lightingmodule using one or more of the phosphor-coated light-emitting dies asits light source. In some embodiments, the fabricating the lightingmodule comprises: attaching the one or more of the phosphor-coatedlight-emitting dies to a substrate; applying a transparent and diffusivegel over the substrate and over the one or more phosphor-coatedlight-emitting dies; and installing a diffuser cap over the substrate,the diffuser cap housing the one or more phosphor-coated light-emittingdies and the transparent and diffusive gel within.

In some embodiments, the plurality of conductive pads are located on asubmount, and wherein the separating includes dividing the submount intoa plurality of submount pieces so that each phosphor-coatedlight-emitting die is attached to a respective submount piece.

In some embodiments, each of the conductive pads includes a lead frame.

In some embodiments, the plurality of conductive pads is attached to asubstrate through a tape, and further comprising: removing the tape andthe substrate before the separating.

In some embodiments, the light-emitting dies include light-emittingdiodes (LEDs).

Another one of the broader forms of the present disclosure involves amethod of packaging a light-emitting diode (LED). The method includes:providing a group of metal pads and a group of LEDs, wherein the metalpads include lead frames; attaching the group of LEDs to the group ofmetal pads, wherein each LED is spaced apart from adjacent LEDs afterthe attaching; coating a phosphor film around the group of LEDscollectively, wherein the phosphor film is coated on top and sidesurfaces of each LED and between adjacent LEDs; and performing a dicingprocess through portions of the phosphor film located between adjacentLEDs to divide the group of LEDs into a plurality of individualphosphor-coated LEDs.

In some embodiments, the attaching is performed so that each LED isattached to two of the respective metal pads that are physicallyseparated from each other.

In some embodiments, for each LED: one of the two metal pads is attachedto a p-terminal of the LED, and the other one of the two metal pads isattached to an n-terminal of the LED.

In some embodiments, the providing the group of LEDs includes: obtaininga plurality of LEDs; assigning the plurality of LEDs into different binsaccording to their performance characteristics; and choosing one or morebins of LEDs as the group of LEDs.

In some embodiments, the providing, the attaching, the coating, and thedicing are performed in a substrate-less manner.

In some embodiments, the LEDs are substantially evenly spaced apartafter the attaching.

In some embodiments, the method further includes applying solder pasteon the metal pads before the attaching

Yet another one of the broader forms of the present disclosure involvesa light-emitting diode (LED) lighting apparatus. The LED lightingapparatus includes: a substrate; a plurality of additionalphosphor-coated LED chips that are located on the substrate, wherein theLED chips are physically separated from adjacent LED chips, and whereineach LED chip includes: an LED die; two conductive pads each bonded tothe LED die; and a phosphor film coated conformally around the LED die,such that the LED die has the phosphor film coated on its top and sidesurfaces.

In some embodiments, the LED lighting apparatus further includes: athermal dissipation structure thermally conductively coupled to thesubstrate; a diffuser cap located over the substrate and housing the LEDchips underneath; and an optical gel disposed between the LED chips andthe diffuser cap.

One aspect of the present disclosure involves a method. The methodinvolves: providing a plurality of light-emitting dies disposed over asubstrate; applying a phosphor material on the plurality oflight-emitting dies; removing the substrate after the applying thephosphor material; and performing a dicing process to the plurality oflight-emitting dies after the substrate has been removed.

In some embodiments, the method further includes: reusing the substratefor a future fabrication process.

In some embodiments, the method further includes: molding the phosphormaterial before the substrate has been removed so that a portion of thephosphor material disposed over each light-emitting die has a dome-like,curved, V or W shape.

In some embodiments, the substrate includes one of: a glass substrate, asilicon substrate, a ceramic substrate, and a gallium nitride substrate.

In some embodiments, the providing is performed such that an adhesivetape is disposed between the substrate and the plurality oflight-emitting dies. In some embodiments, the method further includes:removing the tape; and attaching, after the substrate and the tape havebeen removed and before the dicing process is performed, a differenttape to the plurality of light-emitting dies.

In some embodiments, the method further includes: curing the phosphormaterial before the substrate has been removed.

In some embodiments, the light-emitting dies include light-emittingdiodes (LEDs) that have undergone a binning process.

In some embodiments, the method further includes, before the attaching:fabricating a lighting module with one or more of the light-emittingdies as its light source.

Another aspect of the present disclosure involves a method of packaginglight-emitting diodes (LEDs). The method involves: attaching a tape to aplurality of LEDs, the tape being disposed on a substrate; coating aphosphor film around the plurality of LEDs; curing the phosphor film;removing the substrate after the curing; and singulating the LEDs afterthe substrate has been removed.

In some embodiments, the method further includes: recycling thesubstrate for a future LED packaging process.

In some embodiments, the method further includes: configuring, beforethe substrate has been removed, a shape of the phosphor film with amolding apparatus. In some embodiments, the configuring is performed sothat the phosphor film is shaped to have a plurality of domes, andwherein the domes are disposed over the LEDs, respectively.

In some embodiments, the substrate includes one of: a glass substrate, asilicon substrate, a ceramic substrate, and a gallium nitride substrate.

In some embodiments, the method further includes: before the singulatingthe LEDs: removing the tape; replacing the removed tape with a differenttape.

In some embodiments, the singulating comprises a mechanical die-sawprocess.

In some embodiments, the method further includes: performing a binningprocess to a group of LEDs; and thereafter selecting a subset of thegroup of LEDs as the plurality of LEDs to be attached to the tape.

Another aspect of the present disclosure involves a method offabricating light-emitting diodes (LEDs). The method involves: providinga plurality of LEDs disposed over an adhesive tape, the tape beingdisposed on a substrate, wherein the substrate includes one of: a glasssubstrate, a silicon substrate, a ceramic substrate, and a galliumnitride substrate; coating a phosphor layer over the plurality of LEDs;curing the phosphor layer; removing the tape and the substrate after thecuring; attaching a replacement tape to the plurality of LEDs;performing a dicing process to the plurality of LEDs after the substratehas been removed; and reusing the substrate for a future LED packagingprocess.

In some embodiments, the method further includes molding the phosphorlayer such that the phosphor layer has a plurality of curved segmentsthat are each disposed over a respective one of the LEDs.

In some embodiments, the providing comprises: selecting the plurality ofLEDs from a group of LEDs that are associated with a plurality of bins,and wherein the plurality of LEDs selected all belong to a subset of theplurality of bins.

Yet another aspect of the present disclosure involves a method ofpackaging light-emitting diodes (LEDs). The method includes: attaching atape to a plurality of LEDs, the tape being disposed on a substrate;coating a phosphor film around the plurality of LEDs; curing thephosphor film; removing the substrate after the curing; and singulatingthe LEDs after the substrate has been removed.

In some embodiments, the removing the substrate is performed in a mannersuch that the substrate can be recycled.

In some embodiments, the method includes: molding, before the substratehas been removed, a shape of the phosphor film with a molding stencil.In some embodiments, the molding is performed so that the phosphor filmis shaped into a plurality of portions that each have one of thefollowing shapes: a concave V-shape, a concave W-shape, and a concaveU-shape, plurality of domes, and wherein each portion of the phosphorfilm is disposed over a different one of the LEDs, respectively. In someembodiments, the method may further include: forming a reflective layerover the phosphor film after the curing the phosphor film but before theremoving the substrate. In some embodiments, the molding is performed sothat the phosphor film is shaped into a plurality of portions that eachhave a convex dome-like shape, and wherein each portion of the phosphorfilm is disposed over a different one of the LEDs, respectively.

In some embodiments, the singulating further comprises: mechanicallysawing an area between LEDs to separate the LEDs.

In some embodiments, the method further includes: binning a group ofLEDs into a plurality of bins; and thereafter selecting LEDs in a subsetof the plurality of bins as the plurality of LEDs to be attached to thetape.

Another aspect of the present disclosure involves a method offabricating light-emitting diodes (LEDs). The method includes: providinga plurality of LEDs disposed over an adhesive tape, the tape beingdisposed on a substrate, wherein the substrate includes one of: a glasssubstrate, a silicon substrate, a ceramic substrate, and a galliumnitride substrate; coating a phosphor layer over the plurality of LEDs,the phosphor layer containing multiple sub-layers; curing the phosphorlayer; forming a reflective layer over the phosphor layer; de-taping thetape after the forming of the reflective layer; removing the substrateafter the forming of the reflective layer, the removing the substratebeing performed in a manner such that the substrate is re-usable;attaching a replacement tape to the plurality of LEDs; and performing adicing process to the plurality of LEDs after the substrate has beenremoved.

In some embodiments, one of the sub-layers of the phosphor layercontains a gel mixed with phosphor particles, and the other one of thesub-layers contains a gel mixed with diffuser particles.

In some embodiments, one of the sub-layers of the phosphor layercontains yellow phosphor particles mixed with a gel, and the other oneof the sub-layers contains red phosphor particles mixed with a gel.

In some embodiments, the reflective layer contains silver or aluminum.

In some embodiments, the method further includes: molding the phosphorlayer such that the phosphor layer has a plurality of predeterminedsegments that are each disposed over a respective one of the LEDs. Insome embodiments, the predetermined segments each have one of: a concaveV-shape, a concave U-shape, and a concave W-shape. In some embodiments,the predetermined segments each have a convex dome-like shape.

In some embodiments, the providing comprises: selecting the plurality ofLEDs from a group of LEDs that are associated with a plurality of bins,and wherein the plurality of LEDs selected all belong to a subset of theplurality of bins.

Another aspect of the present disclosure involves a lighting apparatus.The lighting apparatus includes: a white light-emitting die thatincludes: a first-type semiconductor layer; a light emitting layerdisposed over the first-type semiconductor layer; a second-typesemiconductor layer disposed over the light emitting layer; twoconductive terminals disposed on a surface of the second-typesemiconductor layer away from the first-type semiconductor layer; and aphosphor film under which the first-type semiconductor layer, the lightemitting layer, the second-type semiconductor layer, and the twoconductive terminals are covered, wherein the phosphor film includes afirst sub-layer and a second sub-layer disposed over the firstsub-layer.

In some embodiments, the first sub-layer contains a gel mixed withphosphor particles, and the second sub-layer contains a gel mixed withdiffuser particles.

In some embodiments, the first sub-layer contains yellow phosphorparticles mixed with a gel, and the second sub-layer contains redphosphor particles mixed with a gel.

In some embodiments, the phosphor film has a convex dome-like shape.

In some embodiments, the phosphor film has one of the following shapes:a concave V-shape, a concave U-shape, or a concave W-shape. In someembodiments, the lighting apparatus further includes a reflective layerdisposed over the phosphor film.

In some embodiments, a refractive index of the phosphor film is in arange from about 1.4 to about 2.0.

In some embodiments, the lighting apparatus further includes: asupporting member on which a plurality of the white light-emitting diesare located. In some embodiments, the lighting apparatus furtherincludes a housing inside which the supporting member and the pluralityof white light-emitting dies are located. In some embodiments, thehousing is configured for one of: a light bulb, a light tube, a parlight, and a down light. In some embodiments, the plurality of whitelight-emitting dies are arranged in a row. In some embodiments, theplurality of white light-emitting dies are arranged in matrix.

Another aspect of the present disclosure involves a lighting apparatus.The lighting apparatus includes a first doped semiconductor layer. Alight-emitting layer is disposed over the first doped semiconductorlayer. A second doped semiconductor layer is disposed over thelight-emitting layer. The second doped semiconductor layer has adifferent type of conductivity than the first doped semiconductor layer.A photo-conversion layer is disposed over the second doped semiconductorlayer and over side surfaces of the first and second doped semiconductorlayers and the light-emitting layer. The photo-conversion layer has anangular profile.

Another aspect of the present disclosure involves a lighting apparatus.The lighting apparatus includes a light-emitting die. The light-emittingdie includes: a first doped semiconductor layer; a light-emitting layerlocated over the first doped semiconductor layer; a second dopedsemiconductor layer located over the light-emitting layer, wherein thefirst and second doped semiconductor layers have different types ofconductivity; and a first conductive terminal and a second conductiveterminal each located below the first doped semiconductor layer. Thephosphor layer is coated around the light-emitting die. Thephoto-conversion layer has one or more angular corners.

Another aspect of the present disclosure involves a lighting apparatus.The lighting apparatus includes a substrate. One or more light-emittingdiode (LED) dies are disposed over the substrate. The LED dies eachinclude: a first doped III-V compound layer; a multiple quantum well(MQW) layer disposed over the first doped III-V compound layer; a seconddoped III-V compound layer disposed over the MQW layer, wherein thefirst and second doped III-V compound layers have different types ofconductivity. One or more phosphor coatings are each wrapped around arespective one of the one or more LED dies. The phosphor coatings eachhave one or more sharp corners that are defined by an upper surface andside surfaces of the phosphor coatings.

Another aspect of the present disclosure involves a lighting apparatus.The lighting apparatus includes a first doped semiconductor layer. Alight-emitting layer is disposed over the first doped semiconductorlayer. A second doped semiconductor layer is disposed over thelight-emitting layer. The second doped semiconductor layer has adifferent type of conductivity than the first doped semiconductor layer.A first conductive terminal and a second conductive terminal are eachdisposed below the first doped semiconductor layer. A photo-conversionlayer is disposed over the second doped semiconductor layer and on sidesurfaces of the first and second doped semiconductor layers and thelight-emitting layer. A bottommost surface of the photo-conversion layeris located closer to the second doped semiconductor layer than bottomsurfaces of the first and second conductive terminals.

Another aspect of the present disclosure involves a lighting apparatus.The lighting apparatus includes a light-emitting die. The light-emitteddie includes a first doped semiconductor layer. A light-emitting layeris located over the first doped semiconductor layer. A second dopedsemiconductor layer is located over the light-emitting layer. The firstand second doped semiconductor layers have different types ofconductivity. A first conductive terminal and a second conductiveterminal are each located below the first doped semiconductor layer. Aphosphor layer is coated over an upper surface and side surfaces of thelight-emitting die. A bottommost surface of the phosphor layer islocated above a bottommost surface of the first and second conductiveterminals.

Another aspect of the present disclosure involves a lighting apparatus.The lighting apparatus includes a substrate. One or more light-emittingdiode (LED) dies are disposed over an upper surface of the substrate.The LED dies each include: a first doped III-V compound layer; amultiple quantum well (MQW) layer disposed over the first doped III-Vcompound layer; a second doped III-V compound layer disposed over theMQW layer, wherein the first and second doped III-V compound layers havedifferent types of conductivity; a first metal pad that is electricallycoupled to the first doped III-V compound layer; and a second metal padthat is electrically coupled to the second doped III-V compound layer,wherein the first and second metal pads are disposed on an upper surfaceof the substrate. One or more phosphor layers are each coated over anupper surface and side surfaces of a respective one of the one or moreLED dies. The upper surface of the substrate and bottommost surfaces ofthe one or more phosphor layers define a plurality of gaps that are eachin a range from about 0.1 micron to about 50 microns.

Yet another aspect of the present disclosure involves a lightingapparatus. The lighting apparatus includes a light-emitting device. Thelight-emitting device includes a first doped semiconductor layer. Alight-emitting layer is disposed over the first doped semiconductorlayer. A second doped semiconductor layer is disposed over thelight-emitting layer. The second doped semiconductor layer have adifferent type of conductivity than the first doped semiconductor layer.A photo-conversion layer is coated around the light-emitting device. Alens houses the light-emitting device and the photo-conversion layerwithin. The lens includes a first sub-layer and a second sub-layer. Thefirst and second sub-layers have different characteristics.

Yet another aspect of the present disclosure involves a lightingapparatus. The lighting apparatus includes a light-emitting diode (LED)chip. The LED chip includes a first doped semiconductor layer. Alight-emitting layer is located over the first doped semiconductorlayer. A second doped semiconductor layer is located over thelight-emitting layer. The first and second doped semiconductor layershave different types of conductivity. A phosphor film is coated aroundthe LED chip. A lens covers the LED chip and the phosphor film. The lenshas a transmittance greater than about 90% and a refractive indexbetween about 1.4 and about 2. The lens includes a plurality ofsub-layers. The sub-layers have different material compositions.

Yet another aspect of the present disclosure involves a lightingapparatus. The lighting apparatus includes a substrate. The substrate isa printed circuit board substrate, ceramic substrate, or a coppersubstrate. A plurality of phosphor-coated light-emitting diode (LED)dies are disposed over the substrate. The phosphor-coated LED dies eachinclude: a first doped III-V compound layer; a multiple quantum well(MQW) layer disposed over the first doped III-V compound layer; a seconddoped III-V compound layer disposed over the MQW layer, wherein thefirst and second doped III-V compound layers have different types ofconductivity; and a phosphor film coated on each of the LED dies. Thelighting apparatus includes a plurality of molded lenses that each housea respective one of the phosphor-coated LED dies within. The moldedlenses each have a transmittance greater than about 90% and a refractiveindex between about 1.4 and about 2. The molded lenses each include aplurality of sub-layers. The sub-layers each contain particles havingdifferent characteristics.

Yet another aspect of the present disclosure involves a method. Themethod includes providing a substrate having a layer disposed thereon. Aplurality of light-emitting devices is attached to the layer. A gel isapplied over the substrate, the gel covering the plurality oflight-emitting devices. The gel is shaped into a plurality of lenses.The lenses each cover a respective one of the light-emitting devices.The light-emitting devices are separated from one another. The substrateand the layer are removed.

Yet another aspect of the present disclosure involves a method. Themethod includes forming a layer on a substrate. The layer is an adhesivelayer, or a photoresist layer, or a tape. A plurality of light-emittingdiodes (LEDs) is attached to the substrate through the layer. The LEDsare each coated with a phosphor film. A gel is applied over thesubstrate, the gel covering the plurality of LEDs. The gel is moldedinto a plurality of lenses. The lenses each house a respective one ofthe LEDs therein. The plurality of LEDs are singulated. The substrateand the layer are removed.

Yet another aspect of the present disclosure involves a method. Themethod includes providing a substrate with a tape disposed thereon. Aplurality of phosphor-coated light-emitting diode (LED) dies is attachedto the tape. A gel is applied over the substrate. The gel covers theplurality of LED dies. The gel is molded into a plurality of lenses. Thelenses each house a respective one of the LED dies underneath. Theplurality of LED dies is singulated. The tape and the substrate areremoved. The singulated LED dies are bonded to a printed circuit board.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A lighting apparatus, comprising: alight-emitting device that includes: a first doped semiconductor layer;a light-emitting layer disposed over the first doped semiconductorlayer; and a second doped semiconductor layer disposed over thelight-emitting layer, the second doped semiconductor layer having adifferent type of conductivity than the first doped semiconductor layer;a photo-conversion layer coated around the light-emitting device; and alens that houses the light-emitting device and the photo-conversionlayer within; wherein: the lens includes a first sub-layer and a secondsub-layer; and the first and second sub-layers have differentcharacteristics.
 2. The lighting apparatus of claim 1, wherein: thefirst sub-layer contains phosphor particles; and the second sub-layercontains diffuser particles.
 3. The lighting apparatus of claim 2,wherein the diffuser particles include silica, PMMA, ZrO₂, or silicon.4. The lighting apparatus of claim 1, wherein; the first sub-layercontains first phosphor particles; the second sub-layer contains secondphosphor particles; and the first and second phosphor particles aredifferent color phosphor particles.
 5. The lighting apparatus of claim1, wherein the lens has a transmittance greater than about 90% and arefractive index between about 1.4 and about
 2. 6. The lightingapparatus of claim 1, further comprising a substrate on which thelight-emitting device is disposed.
 7. The lighting apparatus of claim 6,wherein the substrate is a Metal Core Printed Circuit Board (MCPCB)substrate, a ceramic substrate, or a copper substrate.
 8. The lightingapparatus of claim 1, wherein the photo-conversion layer comprises aphosphor film.
 9. The lighting apparatus of claim 1, wherein thelight-emitting device comprises a light-emitting diode (LED) die. 10.The lighting apparatus of claim 9, further comprising a lighting moduleon which the LED die is disposed.
 11. The lighting apparatus of claim10, further comprising a lamp in which the lighting module is disposed.12. A lighting apparatus, comprising: a light-emitting diode (LED) chipthat includes: a first doped semiconductor layer; a light-emitting layerlocated over the first doped semiconductor layer; and a second dopedsemiconductor layer located over the light-emitting layer, wherein thefirst and second doped semiconductor layers have different types ofconductivity; a phosphor film coated around the LED chip; and a lensthat covers the LED chip and the phosphor film, the lens having atransmittance greater than about 90% and a refractive index betweenabout 1.4 and about 2; wherein: the lens includes a plurality ofsub-layers; and the sub-layers have different material compositions. 13.The lighting apparatus of claim 12, wherein: one of the sub-layerscontains phosphor particles but is free of diffuser particles; andanother one of the sub-layers contains diffuser particles but is free ofphosphor particles.
 14. The lighting apparatus of claim 12, wherein; oneof the sub-layers contains yellow phosphor particles; and another one ofthe sub-layers contains red phosphor particles.
 15. The lightingapparatus of claim 12, further comprising a substrate on which thelight-emitting device is disposed, wherein the substrate comprises aMetal Core Printed Circuit Board (MCPCB) substrate, a ceramic substrate,or a copper substrate.
 16. The lighting apparatus of claim 12, whereinthe LED is disposed on a lighting module that is implemented inside alamp.
 17. A lighting apparatus, comprising: a substrate that is aprinted circuit board substrate, a ceramic substrate, or a coppersubstrate; a plurality of phosphor-coated light-emitting diode (LED)dies that are disposed over the substrate, wherein the phosphor-coatedLED dies each include: a first doped III-V compound layer; a multiplequantum well (MQW) layer disposed over the first doped III-V compoundlayer; a second doped III-V compound layer disposed over the MQW layer,wherein the first and second doped III-V compound layers have differenttypes of conductivity; and a phosphor film coated on each of the LEDdies; and a plurality of molded lenses that each house a respective oneof the phosphor-coated LED dies within; wherein: the molded lenses eachhave a transmittance greater than about 90% and a refractive indexbetween about 1.4 and about 2; the molded lenses each include aplurality of sub-layers; and the sub-layers each contain particleshaving different characteristics.
 18. The lighting apparatus of claim17, wherein: one of the sub-layers contains phosphor particles but isfree of diffuser particles; and another one of the sub-layers containsdiffuser particles but is free of phosphor particles.
 19. The lightingapparatus of claim 17, wherein; one of the sub-layers contains yellowphosphor particles; and another one of the sub-layers contains redphosphor particles.
 20. The lighting apparatus of claim 17, furthercomprising a lamp in which the substrate and the one or more LED diesare implemented.